Courtesy names and how are they made

I've been scouring the internet for how these are given/made and have really been stumped by how people make their own or are given them.
As I myself am of Chinese descent but not from mainland China I do have my own Chinese name called 林家銘 where 林 being my surname and all but what would my courtesy name be, any kind soul out there would so kindly help me with it ?